The present invention relates to automatic injectors for delivering medicament to an injection site. In particular, the present invention is directed to an automatic injector assembly for quickly combining a liquid material with a dry material to form a liquid medicament for delivering the medicament to an injection site.
An automatic injector is a device for enabling an individual to self-administer a dosage of medicament into his or her flesh. The medicament is stored in liquid form. The advantage of automatic injectors is that they contain a measured dosage of a liquid medicament in a sealed sterile cartridge and can be utilized for delivering the medicament into the flesh during emergency situations. Another advantage of automatic injectors is that the self-administration of the medicament is accomplished without the user initially seeing the hypodermic needle through which the medicament is delivered and without having the user to manually force the needle into his or her own flesh.
There are drawbacks associated with the storage of medicament in liquid form. Some medicaments are not stable in liquid form. Furthermore, some liquid medicaments typically have a shorter shelf life than their solid counterparts. Others have developed automatic injectors that store the medicament in solid form and a liquid injection solution. These injectors, disclosed for example in U.S. Reissue Pat. No. 35,986, entitled xe2x80x9cMultiple Chamber Automatic Injector,xe2x80x9d (the disclosure of which is incorporated herein specifically by reference), however, require the user of the injector to expedite dissolution of the solid component by manually shaking the liquid component and the solid component immediately prior to injection. This increases the time needed to administer a dose of medicament. Furthermore, the improper mixing of the medicament with the liquid injection solution may release an insufficient dose of medicament. There is a need for an automatic injector that stores medicament in solid form that does not require manual premixing by the user. Furthermore, rapid delivery of the medicament is needed for emergency medical situations (e.g. nerve gas and chemical agent poisoning).
It is therefore an object of the present invention to provide an automatic injector device that stores medicament in a solid form for increased shelf life.
It is another object of the present invention to provide an automatic injector device that automatically mixes a solid medicament with a liquid injection solution upon activation.
It is another object of the present invention to provide an automatic injector device that stores the solid medicament under pressure to enhance dissolution in the liquid injection solution.
Additional objects and advantages of the invention are set forth, in part, in the description which follows, and, in part, will be apparent to one of ordinary skill in the art from the description and/or practice of the invention.
In response to the foregoing challenges, applicants have developed an innovative automatic injection device having both wet and dry storage compartments. The present invention is directed to an automatic injection device containing a pre-loaded charge of medicament for automatically self-administering the medicament upon actuation thereof. The automatic injection device may include a housing assembly, a dry compartment located within the housing for storing a predetermined dry charge of the medicament therein, a wet compartment within the housing for storing a predetermined amount of liquid injection solution therein, and an activation assembly for causing the liquid injection solution in the wet compartment to be transferred to the dry compartment. In accordance with the present invention, the medicament located within the dry compartment dissolves in the liquid injection solution as the liquid injection solution passes through the dry compartment to the needle.
The automatic injector in accordance with the present invention further includes at least one compression assembly for maintaining the medicament located in the dry compartment under a continuous compressive state as the liquid injection solution passes through the dry compartment. As such the undissolved medicament is maintained in a compressive state. In accordance with the present invention, the at least one compression assembly is located within the dry compartment. Each compression assembly may include an expandable assembly. The expandable assembly expands as the medicament located within the dry compartment dissolves within the liquid injection solution. The expandable assembly may include a spring assembly and at least one plate to apply pressure on the medicament within the dry compartment. The at least one plate permits the passage of the liquid injection solution therethrough.
The automatic injector in accordance with the present invention further includes a needle assembly for dispensing the liquid injection solution containing the medicament dissolved therein.
The automatic injector in accordance with the present invention may further include a releasable liquid barrier assembly located between the wet compartment and the dry compartment for selectively preventing passage of the liquid injection solution from the wet compartment to the dry compartment at predetermined conditions. It is contemplated that the releasable liquid barrier assembly permits the passage of the liquid injection solution to the dry compartment in response to a predetermined liquid pressure build up within the wet compartment.
In another aspect of the invention, a method for administering an injection of medicament injection solution to a patient using an automatic injection device is provided. Generally, the method comprising locating an injection end of the automatic injection device adjacent a desired injection site on the patient; and activating a drive to advance a collet into a wet compartment of the automatic injection device to pressurize the liquid injection solution in the liquid compartment and to cause an injection needle of the automatic injection device to advance and protrude through the injection end of the automatic injection device. The pressurization of the liquid injection solution causes the liquid injection solution to pass into a dry compartment adjacent the wet compartment where the liquid injection solution mixes with a compressed dry medicament to form a medicament injection solution which is then transmitted through the injection needle to the injection site where it is administered to the patient.